Democrat Senator Carl Levin, chairman of the Armed Services Committee, has called for an international naval blockade of Iranian oil exports. He said the action should be taken before the U.S. and Israel attack Iran.

“I think (these are) options that whoever is willing to participate should explore, including Israel and including the United States,” Levin told C-Span on Friday.

A naval blockade is considered an act of war.

In order to minimize the impact on world oil prices, Levin said alternative oil supplies should be put into place before the blockade. Iran is the number two OPEC oil producer. The EU has agreed on an oil purchase embargo scheduled to begin on July 1.

If sanctions do not force Iran to drop its nuclear program, a “strike is likely” within “months,” Levin warned. He said an Israeli missile system installed by the United States had minimized Iran’s ability to retaliate against Israel after an attack.